The present invention relates to a center core of a magnetic disc that is fixed to the central portion of a flexible magnetic recording media housed within a magnetic disc cartridge, particularly those of high capacity.
Conventionally, magnetic disc cartridges of a construction in which a magnetic disc, formed by magnetic layers being formed on both sides of a flexible polyester sheet or the like and having a metallic center core fixed to the central portion of said flexible magnetic recording media are being utilized mainly as recording media for computers. These so-called floppy disks are rotatively driven and magnetic recording is performed on the aforementioned magnetic layers by a magnetic head. These floppy disks have the advantages of being easy to handle, and low cost.
The aforementioned center core supports the magnetic recording media and defines its center of rotation. The center core also serves the function of transmitting the rotational driving force imparted thereon by a chucking portion provided on the tip of a rotation spindle of a drive side rotational drive means, by which it is held. Normally, the aforementioned center core comprises a discoid standardizing surface portion formed in the central portion thereof that abuts the tip portion of the aforementioned spindle to perform standardizing positioning, and a flanged collar portion formed parallel to the standardizing surface portion at the outer periphery thereof that is fixed to the central portion of the magnetic recording media.
The standardizing surface portion is provided with a central aperture into which the central pin of the spindle is inserted. At the same time, a drive pin of the spindle is engaged with a drive aperture which is provided towards the outside from the aforementioned central aperture, and the center core is to be rotationally driven thereby. Further, a magnet is provided at the tip of the spindle that provides a magnetic attraction force to magnetically attract the center core to supplement maintenance of the chucking state.
With regard to magnetic recording media such as that of the magnetic disc described above, as the recording capacity increases, it becomes necessary to rotate the magnetic disc at high speed in order to secure a transfer rate thereof. In addition, the expected recordation/reproduction performance is secured by the strict maintenance of appropriate relative positioning between the magnetic recording media that rotates at high speed and the magnetic head that performs recordation/reproduction.
It has been proposed to increase the magnetic attraction of the center core to the magnet of the aforementioned spindle in order to stably rotate the magnetic disc at high speed. However, it is difficult from a manufacturing standpoint to accurately form the surface of the magnet at a predetermined height. Also, the accuracy in height becomes unstable if the center core and the magnet are magnetically attached in a state of contact. Therefore, to approach the bottom surface of the center core towards the magnet with a predetermined distance therebetween and attracting the center core in this manner is being considered.
However, if the magnetic attraction force is strengthened towards conventional magnetic discs having a lower recording capacity as well, there is a fear that chucking malfunctions will occur. Therefore, for center cores magnetic discs that have high recording capacities, it has been proposed to form the portion of the bottom surface that faces the magnet of the spindle lower than the central standardizing surface portion thereof to approach the surface of the magnet.
That is, a center core formed in this manner comprises a central standardizing surface portion that abuts the tip surface of a spindle to perform standard positioning; an attraction surface portion formed parallel to and of a different height than the standardizing surface around the outer periphery thereof via a step portion that faces the magnet of the spindle; and a collar portion formed around the outer periphery thereof parallel to the aforementioned standardizing surface portion that is fixed to the magnetic recording media.
In addition, a center core formed in this manner comprises a collar portion of the outer periphery thereof, a standardizing surface portion towards the center thereof, an attraction surface portion around the outer periphery of the standardizing surface portion, and a connection portion that connects the attraction surface portion with the collar portion.
However, as a center core as described above is formed with an attraction surface between a standardizing surface portion and a collar portion of a different height therefrom, multiple drawing processes are required in the manufacture thereof. This causes difficulties in securing manufacturing accuracy with regard to the height positioning accuracy of the standardizing surface portion and the collar portion as well as the degree of parallelism therebetween. This in turn causes problems in securing positional accuracy between the magnetic recording media and the magnetic head.
Particularly in the case that the step between the aforementioned attraction surface and the standardizing surface is on the order of a board thickness, there is a propensity for the manufacturing accuracy to be difficult to obtain with regard to a drawing process. A higher degree of parallelism is required, as there is a fear that vertical movement of the magnetic recording media will be generated along with the rotation of the aforementioned magnetic disc.
The present invention has been developed in view of the circumstances described above, and it is a first object of the present invention to provide a center core for a magnetic disc that enables stable high speed rotation of a magnetic recording media, said center core being provided with a stepped formed portion between the standardizing surface portion and the attraction surface, formed by multiple drawing processes, wherein manufacturing accuracy is obtained, and parallelism between the standardizing surface portion and the collar portion, as well as dimensional accuracies thereof are secured.
It is a second object of the present invention to provide a center core for a magnetic disc that enables stable high speed rotation of a magnetic recording media, said center core having improved dimensional accuracies of the standardizing surface portion and the attraction surface, as well as securing parallelism between the standardizing surface portion and the collar portion, as well as dimensional accuracies thereof.
By the attraction surface being formed lower than the standardizing surface portion in a center core as described above, during a state in which a magnetic disc is housed within a case, the aforementioned attraction surface portion protrudes from the hub aperture of said case. This causes a fear that if said case is dropped or the like, the impact will act directly thereon and damage the magnetic recording media.
That is, when the magnetic disc cartridge is in a horizontal state, the standardizing surface portion as well as the attraction surface portion of the aforementioned center core protrudes from the bottom surface of the case. At a time when the disc is dropped or the like, the attraction surface portion of the center core collides with an external member such as a floor, the impact is transmitted directly to the magnetic recording media, and the magnetic recording media suffers damage by colliding with the internal surface of the case. Particularly in a case that the impact on the aforementioned attraction surface portion acts thereon in an oblique manner and the magnetic recording media collides with the internal surface of the case in an oblique manner, the magnetic recording media is more likely to be damaged.
The present invention has been developed in view of the above described circumstances, and it is a third object of the present invention to provide a center core for a magnetic disc that prevents damage to the magnetic recording media by cushioning the impact suffered by the attraction surface portion.
A center core for a magnetic disc according to the present invention that achieves the first object described above is a center core for a magnetic disc which is held by the magnetic attraction force of a magnet provided at the tip of a spindle, said spindle transmitting a rotational driving force to said center core. The center core comprises: a standardizing surface portion formed as a disc in the central portion thereof, that abuts the tip surface of the aforementioned spindle to perform standardizing positioning; an attraction surface portion formed annularly around the outer periphery of said standardizing surface portion via a step portion so that it is parallel to the standardizing surface portion while of a different height, that faces the aforementioned magnet provided at the spindle; and a collar portion formed as a flange around an outer periphery thereof, parallel to said standardizing surface portion, that is fixed to the central portion of a discoid magnetic recording media; wherein the step portion between the standardizing surface portion and the attraction surface portion is of a multiple step drawn form.
It is preferable that the height of each drawn step of the step portion between the standardizing surface portion and the attraction surface is less than or equal to xc2xd the board thickness.
According to the center core that achieves the first object of the present invention as described above, by forming the step portion, between the standardizing surface portion that abuts the tip surface of the spindle to perform standardizing positioning and the attraction surface portion that faces the magnet of the spindle, in a multiple step drawn form, the manufacturing accuracies thereof are improved. Accordingly, parallelism as well as dimensional accuracies of the standardizing surface portion and the peripheral collar portion to which a magnetic recording media is fixed is secured. Therefore, stable high speed rotation is obtained, enhancing the reliability of the magnetic recordation/reproduction characteristic of a high recording capacity magnetic recording media.
A center core for a magnetic disc according to the present invention that achieves the second object described above is a center core for a magnetic disc which is held by the magnetic attraction force of a magnet provided at the tip of a spindle, said spindle transmitting a rotational driving force to said center core. The center core comprises: a collar portion formed as a flange on the outer periphery thereof, to which a discoid magnetic recording media is fixed; a standardizing surface portion formed as a disc in a central portion thereof, that abuts the tip surface of the aforementioned spindle to perform standardizing positioning; an attraction surface portion formed annularly around an outer periphery of said standardizing surface portion while lower than said standardizing surface portion, that faces the aforementioned magnet provided at the spindle; and a link portion that links said attraction surface portion and the collar portion; wherein the aforementioned standardizing surface portion and attraction surface portion are formed separately then are joined to each other.
It is preferable that the height of the step between the standardizing surface portion and the attraction surface is formed to be equal to the board thickness of said attraction surface portion.
It is preferable that the link portion a swell as the collar portion are formed integrally on the attraction surface portion. The standardizing surface portion and the attraction surface portion maybe formed separately utilizing different materials. The standardizing surface portion and the attraction surface portion are joined by spot welding or the like.
According to the center core that achieves the second object of the present invention as described above, by forming the standardizing surface portion, that abuts the tip surface of the spindle to perform standardizing positioning, and the attraction surface portion, that faces the magnet of the spindle, separately then joining them, a drawing process of a board thickness between the two portions is obviated, thereby improving and stabilizing the dimensional accuracies thereof. Accordingly, parallelism as well as dimensional accuracies of the standardizing surface portion and the peripheral collar portion, to which a magnetic recording media is fixed is secured. Therefore, stable high speed rotation is obtained, enhancing the reliability of the magnetic recordation/reproduction characteristic of a high recording capacity magnetic recording media.
Particularly if the step between the standardizing surface portion and the attraction surface portion is formed to be a board thickness of the attraction surface portion, further improvements in parallelism and dimensional accuracies can be obtained.
A center core for a magnetic disc according to the present invention that achieves the second object described above is a center core for a magnetic disc which is held by the magnetic attraction force of a magnet provided at the tip of a spindle, said spindle transmitting a rotational driving force to said center core. The center core comprises: a collar portion formed as a flange on the outer periphery thereof, to which a discoid magnetic recording media is fixed; a standardizing surface portion formed as a disc in a central portion thereof, that abuts the tip surface of the aforementioned spindle to perform standardizing positioning; an attraction surface portion formed annularly around an outer periphery of said standardizing surface portion while lower than said standardizing surface portion, that faces the aforementioned magnet provided at the spindle; and a link portion that links said attraction surface portion and the collar portion; wherein the attraction surface portion is provided with an impact absorption member.
It is preferable that the impact absorption member be of a construction in which a plastic film, foam film, or the like are fixed on an outer surface of the attraction surface portion and/or the inner portion of the attraction surface portion is filled with a high viscosity impact absorption material such as foam.
According to the center core that achieves the third object of the present invention as described above, by providing the attraction surface portion with an impact absorption member, the impact suffered by the case when it collides with, for example, a floor, in case it is dropped or the like is absorbed and cushioned by the impact absorption member. Accordingly, the force with which the magnetic recording media collides with the internal surface of the case is reduced, thereby preventing the occurrence of damage thereto. Therefore, the reliability of the magnetic recordation/reproduction characteristic of a high recording capacity magnetic recording media is enhanced.